Denver Mint correspondence scanned at the National Archives (NARA) in Denver - covering the period 1935-1937. NARA identifier is record group 104, 8KRA-104-84-051. Box 1, Folder 16. Folder 16 title: “… Materials Approval Denver …” Courtesy of John Graffeo.
While some of the folders in this respective sequence were already numbered and others were not - new numbers were assigned to each folder based on the archival theory of original order - which is strongly respected and maintained by NARA. These new numbers are represented in the metadata, and again - they represent the order in which the folders were found in the archival boxes to which they belong.